The present application relates generally to markers for surgically implanting within the tissues of a patient to mark the location of a lesion. More specifically, the present invention relates to a marker which is mechanically self-anchoring within the target tissue and which can be delivered through a relatively small gauge needle.
Advances in modern medical imaging technologies such as X-ray, ultrasound, or magnetic resonance imaging make it possible to identify and to biopsy tumors while they are still small. When dealing with a small tumor, especially after a portion of the tumor has been removed for biopsy, it is sometimes difficult to relocate the tumor at a later time for treatment. This is particularly true in the case of tumors in the breast, where the ability to visualize a small growth may depend upon the manner in which the breast is positioned or compressed during the procedure. In addition, prior to surgically removing a tumor, it is often advantageous to try to shrink the tumor by chemotherapy or irradiation. This is especially true in the case of breast cancer, where conservation of breast tissue is a concern. Shrinkage of the tumor can sometimes make it difficult for the surgeon to locate the tumor. It is therefore often desirable to place a marker within the target tissues at the time of biopsy which can be visualized under a variety of imaging modalities to facilitate finding the tumor at a later time.
For such a marker to be effective, it must be visible under a variety of imaging modalities and must maintain its position within the tissues. Implants placed loose within the tissues have a tendency to migrate, and this tendency is particularly acute in the case of fatty tissue, such as the breast. Accordingly, for such a marker to resist migration, it must clamp or otherwise attach to the target tissues. One device which is currently being used is implanted into the target tissues and then manipulated remotely by means of wires to cause the implant to clamp to the target tissue. However, the manipulation of the wires to clamp the device to the target tissues complicates the deployment procedure. Further, it is possible that the wire may not properly detach from the implant.
Another device which is currently in use involves a C-shaped or U-shaped marker which is implanted and then crimped with a pliers-like instrument to attach the marker to the tissue. However, this process also requires affirmative intervention by the physician beyond simply guiding the marker to the desired location, namely, the step of crimping the marker to anchor it to the tissues. Thus, there is a need for a marker which automatically mechanically attaches to the target tissues upon being deployed, without the need for intervention by the surgeon.
Because of advances in biopsy technology, it is possible to biopsy suspicious tissue with a fourteen or even sixteen gauge or smaller needle. Use of such a small gauge needle minimizes patient discomfort and makes it possible to retrieve the biopsy specimen through a small incision. Since a marker which can be implanted only through a larger needle or incision, or which would require a larger instrument to crimp the anchor to the tissues, would largely defeat the advantages of needle biopsy, there is a need for a marker as well as an apparatus and method for implanting the marker which is capable of implanting and anchoring the marker by way of an instrument no larger in diameter than the needle used for biopsy purposes.
Stated generally, the present invention comprises a marker for implanting in the tissues of a patient, such as at the time of a biopsy, to facilitate locating the site at a future date. The marker is self-anchoring, automatically mechanically attaching to the target tissues upon being deployed without the need for intervention by the, surgeon. The marker is capable of being implanted through a needle no larger than the needle used for biopsy purposes.
Stated somewhat more specifically, the present invention comprises a marker for inserting by a physician through a lumen of a hollow needle to a target site within the tissues of a patient to facilitate locating the target site at a later time. The marker is capable of assuming an essentially linear configuration for passage through the hollow needle. The marker includes means for anchoring itself to the tissues of the patient without intervention by the physician.
In a first aspect the marker is comprised of a shape memory alloy having a phase change temperature which is higher than normal room temperature but lower than the normal body temperature of the patient. When the marker is exposed to a temperature below the phase change temperature, the marker can be configured into an elongated, essentially linear configuration for passage through the needle. When the marker is exposed to a temperature higher than the phase change temperature, such as by exposure within the tissues of the patient, the marker assumes a predetermined configuration which will anchor it to the tissues of the patient without intervention by the physician. According to one embodiment, the marker assumes a helical shape upon being exposed to a temperature higher than its phase change temperature. In another embodiment the marker assumes a ring shape.
In another aspect, the marker is comprised of a plurality of wires whose free ends form barbs. The barbs are normally bent outward but can be deformed into an essentially linear configuration for passage of the marker through a hollow needle. Upon the marker exiting the forward end of the needle the barbs spring outward, anchoring the marker to the tissue. According to one embodiment, two or more wires are anchored within a tubular body portion with their free ends extending from either end of the tubular body portion to form the barbs. In another embodiment, the central portions of two or more wires are twisted together, with the free ends of the wires forming barbs. In yet another embodiment, the central portions of two or more wires are bonded together, such as by welding, adhesives, heat shrink tubing, or other biocompatible method, with the free ends of the wires configured into barbs.
The invention further includes a method for implanting a plurality of markers within the tissues of a patient. A plurality of markers of the type previously described are sequentially loaded into a hollow needle. A stylet is inserted into the rearward end of the hollow needle to push the markers through the needle and out its forward end. According to the method of the invention the forward end of the needle is positioned at a first location, and the stylet is advanced to eject a first marker from the forward end of the needle and into the tissues of the patient. The forward end of the needle is then repositioned to a second location without withdrawing the needle from the patient, and the stylet is further advanced to eject a second marker from the forward end of the needle and into the tissues of the patient.
Thus it is an object of the present invention to provide an improved marker for implanting in the tissues of a patient, such as at the time of a biopsy, to facilitate locating the site at a future date.
It is another object of the present invention to provide a marker which is automatically self-anchoring without the need for intervention by the surgeon.
Still another object of the present invention is to provide a marker which can be visualized under a variety of imaging modalities and yet which can be implanted through a needle no larger than the needle used for biopsy purposes.
Other objects, features, and advantages of the present invention will become apparent upon reading the following specification, when taken in conjunction with the drawings and the appended claims.